Novel approaches for reducing cognitive decline in older adults are needed given the aging of the population and the personal, socioeconomic, and public health implications of cognitive impairment in older adults. Epidemiologic data now strongly suggest that age-related peripheral hearing loss in older adults is independently associated with accelerated cognitive decline and incident dementia. Mechanistic pathways that could underlie this observed association include the effects of poor audition and distorted peripheral encoding of sound on cognitive load and/or reduced social engagement. These pathways may be amenable to comprehensive hearing rehabilitative treatment consisting of the use of hearing assistive technologies (hearing aids, other integrated hearing assistive devices) and rehabilitative training. To date, however, there has never been a randomized trial that has investigated whether hearing loss treatment could reduce cognitive and other functional declines in older adults. We propose to develop such a clinical trial that will have the following specific aims: Clinical Trial Aim #1: To determine the effects of best-practices hearing loss treatment on rates of cognitive decline (primary outcome measure) in 70-79 year-old well-functioning and cognitively-normal older adults with hearing loss. Clinical Trial Aim #2 To determine the effects of best-practices hearing loss treatment on secondary outcome measures of health-related quality of life, social/leisure activities, daily functioning, mobility, and longitudinal brain atrophy on structural MRI. Clinical Trial Aim #3: To investigate the mechanistic pathways through which hearing loss treatment affects cognitive functioning by studying longitudinal changes in proximal/mediating outcome measures in relation to cognitive trajectories. In order to design and plan this clinical trial, we have assembled a diverse, multidisciplinary team of experts who span the fields of cognitive aging/gerontology and otolaryngology/audiology. We will build upon the substantial existing resources of the Atherosclerosis Risk in Communities Neurocognitive Study (ARIC-NCS) that include research infrastructure (established field sites, study personnel, and data coordination center) and a well-characterized cohort of >6000 ARIC-NCS participants who have been followed for >25 years and from which we would recruit trial participants. In addition, we will also draw upon existing trial experience and protocols from the NIA- supported Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) trial. Major activities during the two-year clinical trial planning grant phase include finalizing and pilot testing recruitment and retention strategies, operationalizing and pilot testing the hearing rehabilitative intervention, developing and pilot testing the final outcome battery, writing the manual of procedures, developing the data management system, and preparing the final grant application for the clinical trial.